Replaceable pattern cam for sewing machines

ABSTRACT

An exchangeable sewing machine pattern cam unit including a cam disk portion and having a raised hub providing a finger grip. The unit is fabricated in a two-part mold separable axially of the pattern cam disk. The raised hub is formed with a plurality of radial indentations which terminate short of the upper extremity of the hub leaving segmented lips which enhance the operator&#39;&#39;s grip on the cam unit hub. This advantageous cam hub formation is attained by the method of providing core pins in an ordinary twopart mold which core pins project through the cam disk portion of the cam unit into position for defining the radial indentations in the hub portion of the cam unit.

llnited States Patent Momberg [54] REPLACEABLE PATTERN CAM FOR SEWING MACHINES [151 3,656,369 [451 Apr. 16,1972

Primary Examiner--William F. ODea Assistant Examiner-F. D. Shoemaker Attorney-Marshall .l. Breen, Chester A. Williams, Jr. and

[72] Inventor: James Momberg,Somervi1le, NJ. Robert E Smith [73] Assignee: The Singer Company, New York, N.Y. [22] Filed: Jan. 6, 1971 [57] ABSTRACT An exchangeable sewing machine pattern cam unit including a [21] Appl' l04407 cam disk portion and having a raised hub providing a finger grip. The unit is fabricated in a two-part mold separable axi- [52] US. Cl. ..74/567, 112/158 A ally of the pattern cam disk. The raised hub is formed with a f Cl 6h /00 plurality of radial indentations which terminate short of the Fleld ofSearch upper extremity of the hub leaving segmented which 66/50 156; 112/158 A enhance the o erators rip on the cam unit hub. This ad- P g vantageous cam hub formation is attained by the method of [56] References C'ted providing core pins in an ordinary two-part mold which core UNITED STATES PATENTS pins project through the cam disk portion of the cam unit into position for defining the radial indentations in the hub portion 2,924,l 2O 2/1960 JOhflSOl'l ..74/568 R of the 3am unit 3,214,996 11/1965 Bono ..74/568 R 2 Claims, 4 Drawing Figures I6 48 l8 I7 32 ll 3| a 2 30 m K20 I3 14 the 4E A we W .ha 44 1 42' A W k Wu mm M s 1% 4 i PNENTEDAPR 18 I972 INVETOR. James W. TORNEY Fig.4

8 S E N T W REPLACIEABILIE PATTERN @AM FOR SEWING MACHINES BACKGROUND OF THE INVENTION Exchangeable pattern cam units for sewing machines such as are disclosed in the prior U.S. Pat. No. 2,924,120, Feb. 9, 1960 of R. E. Johnson, are formulated with surfaces extending principally parallel to the axis of the cam unit so that they may be fabricated in two-part'molds. Cam units having hubs so formed are not easy for an operator to grip and previous attempts to provide lips, grooves, rings, or the like, on the hub to improve the grip have necessitated either separate machining steps to cut the grooves after molding or far more complicated and expensive molding techniques.

SUMMARY OF THE INVENTION The exchangeable pattern cam unit of this invention includes a hub portion which is formed with pronounced annular lip segments which greatly enhance an operator's grip on the cam unit for more convenient insertion and removal of the cam unit from the sewing machine. The favorable hub configuration is attained without the necessity for machining or without requiring anything more complicated than a two-part mold by the method of including into the mold core pins which extend through the cam disk portion of the mold well within and not in conflict with the peripheral cam track surfaces of the cam disk portion. The core pins form pronounced radial indentations in the hub portion of the cam unit and terminate short of the free extremity of the hub portion thereby defining the annular lip segments which provide for advantageous grip of the cam unit by a sewing machine operator.

With these and additional objects and advantages in view as will hereinafter appear, this invention will be described with reference to the accompanying drawing of a preferred embodiment in which:

FIG. 1 is a top plan view of an exchangeable sewing machine pattern cam unit made in accordance with this inventron;

FIG. 2 is a perspective view of the pattern cam unit of FIG.

FIG. 3 is a vertical cross-sectional view of the pattern cam unit of FIG. 1 shown in operative position on a cam reception seat atop a pattern cam stack of a sewing machine; and

FIG. 4 is a vertical cross-sectional view of a mold suitable for use in the fabrication of the pattern cam unit of FIG. 1.

Referring to the drawings, an exchangeable pattern cam unit 11 built in accordance with this invention, is illustrated in FIGS. 1 and 2. The pattern cam unit comprises a cam disk portion 12 which is generally circular in shape and is formed with one or more pattern cam tracks 13 and 14 which, as shown in the drawing, may be formed on the periphery of the cam disk portion 12. Projecting from one side of the cam disk portion 12 is a hub portion 15 which is located substantially coaxial with the cam disk portion and terminates in a free'extremity 1 6. The hub portion 15 is formed with a central bore 17 which includes an inwardly extending annular flange 18 which serves to constrain the exchangeable cam unit in place in the sewing machine as will be described below.

Extending transversely through the cam disk portion 12 of the cam unit is an elongate slot 26 which is disposed radially beyond the hub portion 15 and serves, as will be described below, to lock the exchangeable pattern cam unit for rotation with a camshaft in the sewing machine.

The cam disk portion 12 is also formed with a plurality of transverse apertures 30 which are preferably evenly spaced about the axis of the cam disk portion and of which a substantial part of each is overhung by the hub portion 15. As best shown in FIG. 2 the hub portion 15 is formed with a plurality of recesses 31 each arranged in continuation of one of the transverse apertures 30 of the cam disk portion. The recesses 31 terminate short of the free extremity 16 of the hub portion, each recess 31 preferably terminating an identical distance short of the free extremity of the hub portion so as to define like segments 32 of an annular rib about the free extremity of the hub portion 15. The annular rib segments 32 together serve as a finger grip to facilitate manipulation of a cam unit 11 by a machine operator into and out of operative position in a sewing machine.

Referring to FIG. 3, the manner in which a cam unit 11 of this invention is accommodated in a sewing machine will now be explained. Indicated at 40 in FIG. 3 is a stationary cylindrical stud which may be carried in a sewing machine frame and provides a bearing for a hollow camshaft 41. Indicated by phantom lines at 42 is a stack of pattern cam disks which are carried as a unit on the camshaft 41. A pin 43, which is set into the pattern cam disks 42 and extends parallel to the camshaft 41, may be secured onto the assembled pattern cam disks 42 by a flanged collar 44 which seats in a notch 45 in the pin 43 and is retained on the stationary stud 40 by a shouldered fastening screw 46 threaded into the stud 411. A fastening screw 47 may also be provided through the flange collar and threaded into the camshaft 41 to lock the assembled pattern cam disks 42 and pin 43 for rotation together.

The shouldered fastening screw 46 also serves to constrain above the flanged collar 44, a three-armed spring 48 which serves as shown in FIG. 3 to engage the inwardly extending annular flange 18 within the cam unit bore 17 resiliently to restrain a pattern cam in place on the flanged collar 44 above the pattern cam disks 42 and with the aperture 20 embracing the pin 43 so that an exchangeable cam unit 11 so mounted will be drivingly locked upon the camshaft.

The force necessary to depress a cam unit 11 into locked relation with the arms of the three-armed spring 48 and the force necessary to overcome the three-armed spring 48 when it is desired to remove a cam unit 11 is considerable, and exchange of a cam unit can be difficult if an operators fingers slip on the hub portion 15. The annular rib segments 32 about the free extremity of the hub portion 15 of each cam unit made in accordance with this invention provide for a sure grip by an operator on the cam unit and in a manner which does not require subsequent machining operations in the fabrication of the molded cam unit, or which does not require complicated molding or fabricating techniques. The cam unit made in accordance with this invention is, therefore, not appreciably more expensive than cam units made heretofore with smooth hub portions.

FIG. 4 in the drawing illustrates a mold for the fabrication of a cam unit in accordance with this invention and will serve to indicate a novel method for producing a cam unit in accordance with this invention. Shown in FIG. 4 is a two-part mold with the upper part 50 formed with a cavity 51 havingthe shape of the hub portion 15 of the cam unit and a cavity 52 conforming to the shape of a portion of the cam disk portion 12 of the cam unit. A second part 53 of the two-part mold is formed with a cavity 54 conforming to the shape of a portion of the cam disk portion 12, of the pattern cam unit 11. A core pin 55 is illustrated in FIG. 4 set into the mold part 53 in a position substantially parallel to the axis of the pattern cam unit which will be produced in the mold. The core pin 55 extends completely through the mold cavities 52 and 54 for the cam disk portion of the cam unit and continues only partly into the mold cavity 51 for the hub portion of the cam unit. A separate core pin 55 will, of course, be provided for each aperture 30 and recesses 31 which it is desired to include in the cam unit. The method of producing a cam unit in accordance with this invention, therefore, is to provide a mold in two parts, provide the mold with core pins 55, which are arranged substantially parallel to the axis of the cam unit to be produced in the mold with the core pins extending completely through the cam disk forming cavities of the mold and partly through the cam hub cavities of the mold, injecting a plastic material, such as a synthetic resin or other known plastic material, into the closed two-part mold and thereafter separating the mold parts in the direction of the axes of the cam disk and hub portions of the pattern cam unit so as to withdraw the core pins when the mold is open.

With this method of cam unit fabrication, the simplest of molding techniques is utilized, and the expense of pattern cam unit manufacture is thus minimized notwithstanding that a roughened advantageous finger grip is provided on the cam unit hub portion for manipulation by a sewing machine operator.

Having set forth the nature of the invention, what I claim herein is:

1 An exchangeable pattern cam unit for a sewing machine including a cam disk portion formed with a cam track, and a cylindrical hub portion substantially coaxial with and projecting to a free extremity on one side of said cam disk portion, said cam disk portion being formed with a transverse aperture of which a substantial part is overhung by said hub portion,

said hub portion being formed with a recess which is a continuation of said transverse disk portion aperture and which recess terminates short of the free extremity of said hub portion to define a segment of an annular rib at the free extremity of said hub portion to provide a finger grip.

2, An exchangeable pattern cam unit as set forth in claim 1 in which a plurality of said apertures is formed in said cam disk portion in substantially evenly spaced relation around said hub portion and in which the recesses in said hub portion in continuation of each of said plurality of apertures terminate at substantially the same distance from the free extremity of said hub portion. 

1. An exchangeable pattern cam unit for a sewing machine including a cam disk portion formed with a cam track, and a cylindrical hub portion substantially coaxial with and projecting to a free extremity on one side of said cam disk portion, said cam disk portion being formed with a transverse aperture of which a substantial part is overhung by said hub portion, said hub portion being formed with a recess which is a continuation of said transverse disk portion aperture and which recess terminates short of the free extremity of said hub portion to define a segment of an annular rib at the free extremity of said hub portion to provide a finger grip.
 2. An exchangeable pattern cam unit as set forth in claim 1 in which a plurality of said apertures is formed in said cam disk portion in substantially evenly spaced relation around said hub portion and in which the recesses in said hub portion in continuation of each of said plurality of apertures terminate at substantially the same distance from the free extremity of said hub portion. 